Tamping plug for boreholes



March 1965 G. GRIFFITH ETAL 3,173,368

TAMPING PLUG FOR BOREHOLES Filed July 18, 1962 Inventors:

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m fie n f m m m L m m 8H m mu United States Patent 3,173,368 TAMPING PLUG FGR BOREHOLES George L. Griflith, Coopersburg, and Franklin 13. Wells, Emmaus, Pa., assignors to Trojan Powder Company, Allentown, Par.

Filed July 18, 1962, Ser. No. 210,666 4 Claims. (Cl. 102-36) This invention relates to blasting and has for its principal object the provision of a tamping plug which will avoid the use of loose stemming materials while at the same time retaining all of the normal advantages of stemming, clay plugs, or wedged asbestos plus.

A further object of the invention is to provide a tamping plug formed of a plurality of nested units whereby only as many units may be used as a plug for a given borehole as may be required, thus insuring minimum cost.

In the drawings:

FIG. 1 is a sectional view showing a loaded borehole using a tamping plug of our invention.

FIG. 2 is an axial section through a unit of our plug in its preferred form.

FIG. 3 is an end view looking into the borehole at a slightly modified plug formed of units each having a single rib.

The plug of the present invention because of its multiple wedging action when using a plurality of units forms a good seal even in relatively loose soil, is readily placed in position as there is nothing to get out of order, is quite inexpensive, and the units may all be exactly alike although it is preferred that in a multiple unit plug the final unit be slightly larger in brim size than the others.

In FIG. 1 there is shown an explosive catridge 10 which may be the final cartridge of a series located in a borehole 11 which may be large or small, horizontal as illustrated or at any angle, such as an upwardly drilled borehole for which this invention is particularly suited. The lead-in wires 12 follow usual practice leading to an initiating device (not shown). The tamping plug 15 is here shown as consisting of five nested units 16, four of them exactly alike while the final unit 17 may be similar except that its major or brim diameter may be slightly larger in order to insure a very tight seal, this being quite advantageous in cases where there is little or no loose material in the borehole. The word nested is used in its dictionary sense of meaning a group of things lying or set close together that fit within each other.

Referring now to FIG. 2 the units 16 resemble flat brimmed hats of many decades ago, such as those worn by the early Puritans, including a flat circular brim 20, a crown 21 which may be somewhat convex but is preferably flat for economy and convenience of manufacture, and a conical portion 23 joining the brim and crown. The material should be sufliciently flexible to insure against damage to the lead wires 12 as in FIG. 3 and to make a snug fit against the wall of the borehole. We have found units made of polyethylene, polypropylene, and plasticized polyvinyl chloride compositions to be excellent when made by injection molding, compression or similar processes, as units so made retain both their strength and their flexibility for long periods of time and over the temperature ranges to be expected in normal blasting operations; that is, from perhaps as low as -l F. to somewhat over a hundred degrees.

While not essential, considerable improvement is had when the conical portion 23 is ribbed on the outside as at 30 and 31 providing circular grooves 33 and 34 on the inside as this configuration creates a Zone of excess expansion where rib 30 engages the next successive unit close to the brim 26 and also where rib 31 engages groove or valley 34 of the next outer unit 16, thus providing 3,l?3,3%3 Patented Mar. 16, 1955 a positive means for locking the units together to form the plug 15.

It is preferred to have the brirns of the units the exact diameter of the borehole in which they are to be used. In such cases .it will be noted that the first unit to be inserted fits the hole snugly as at 35 but the next brim is a bit more flared as at 36 because of theengagement with rib T10 underneath it; the next brim will be still farther flared as at 37, the next brim having the same flare as at 38 and the ribs now exert the same outward pressure, and so on if more than five units are employed.

The final unit 17 as-stated may, and preferably does, have a flat brim' of greater diameter than the hole as this aids in sealing any existing irregularity of the borehole. The excess diameter could, for a one inch hole, he as great as a quarter inch, bu-t usually al /e unit would be suificiently large. The flare of the final unit as at 39 is appreciably greater than the flares at 38 but would be the same as at 38 if all the units were of the same size as will be used where conditions so suggest.

In the modification shown in FIG. 3 the plug is composed of a plurality of units differing from the preferred form only in that a single rib 40 is used, omitting the second rib of the preferred form shown in FIG. 1. The periphery of the brim 20 is numbered 41.

The plug of the present application is quite versatile, amply holding the charge from becoming dislodged due to vibrations from nearby blasts; for example, completely protecting against entrance of sparks, and being totally disintegrated by the explosion of its charge. The units are made in various weights, thicknesses and diameters but as an illustration, a plug of 2" or less would use a thickness of about two or three thirty-seconds of an inch while increasing to an eighth of an inch for a 5" brim diameter.

Normally a 2" brim diameter unit would have a crown diameter of A", an outside diameter at junction of brim and conical portion of 1%", height of rib A thickness of unit material and height of unit 1, that is half of the brim diameter. The slope of the conical portion is naturally such as to aiiord a snug fit in nesting the units into a tamping plug.

In use, the plug of this invention is inserted into the borehole conventionally; after loading and initiating charges have been set in place, a unit of this invention is placed brim first in contact with the final charge 10, preferably using a hollow end tamping stick, that is one having a recess to fit the unit. Such a cupped stick will insure correct placement of the unit as it will prevent the unit from turning sideways. A second unit, similarly inserted, is forced against the first unit so that the two units are as illustrated in FIG. 1, in which position the peripheral edge of the brim of the second unit becomes slightly deformed as at 36 into the shape of an outwardly directed flare. Further units are added as may be required thus insuring that the plug is pressed very tightly against the wall of the borehole.

What we claim is:

1. In a device for effectively closing a borehole having therein an explosive charge, a tamping plug comprising a plurality of nested hat-like units, each unit comprising a borehole wall engaging, outwardly extending brim having a circular peripheral margin, an imperforate crown forming the top of the hat-like unit, and an imperforate conical portion joining the brim and crown, the conical portions of the units being larger at their junction with the brim than at their junction with the crown, the overall diameter of the brim being considerably greater 553 the diameter of said junction of the conical portion and the brim, the units having the same slope of their conical portions to afford a snug fit of the units when nested in the borehole, and the outside diameter of each 55 outwardly extending brim is about twice the axial length of the unit, the axial length of the tamping plug being varied to suit conditions by assembling as many of the units as may seem desirable for the particular borehole.

2. The plug of claim 1 in which the conical portions of the units are circularly ribbed on the outside with a corresponding groove on the inside to provide means for locking the units together when tamped in the borehole, more strongly than provided by mere friction alone.

3. The plug of claim 1 in which the units are of fexible plastic material and engage the borehole with increasing pressure from the explosive charge outwardly toward the borehole opening, the radial pressure being increased by the provision of a plurality of continuous rounded ribs and corresponding grooves on each unit with the ribs of an inner unit engaging the grooves of the proximate outer unit.

4. The plug of claim 1 in which the units are of a uniform thickness from to 41" depending upon the diameter of the brim, and the diameter of the brim of 4 the final unit is slightly larger than the brim diameter of the initial unit to aid in sealing any existing irregularity of the borehole.

References Cited by the Examiner UNITED STATES PATENTS 921,144 5/09 McGregor u 1023O 2,276,109 3/42 Smith 15-104.06 2,388,232 10/45 Tappan 102-30 2,916,995 12/59 Douglass et al. 10230 3,010,518 11/61 Harmon 166-202 X 3,112,701 12/63 Grebe 102--22 FOREIGN PATENTS 601,517 5/36 Germany 22497 865,025 4/61 Great Britain 220--97 BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner. 

1. IN A DEVICE FOR EFFECTIVELY CLOSING A BOREHOLE HAVING THEREIN AN EXPLOSIVE CHARGE, A TAMPING PLUG COMPRISING A PLURALITY OF NESTED HAT-LIK UNITS, EACH UNIT COMPRISING A BOREHOLE WALL ENGAGING, OUTWARDLY EXTENDING BRIM HAVING A CIRCULAR PERIPHERAL MARGIN, AN IMPERFORATE CROWN FORMING THE TOP OF THE HAT-LIKE UNIT, AT AN IMPERFORATE CONICAL PORTION JOINING THE BRIM AND CROWN, THE CONICAL PORTIONS OF THE UNITS BEING LARGER AT THEIR JUNCTION WITH THE BRIM THAN AT THEIR JUNCTION WITH THE CROWN, THE OVERALL DIAMETER OF THE BRIM BEING CONSIDERABLY GREATER THAN THE DIAMETER OF SAID JUNCTION OF THE CONICAL PORTION AND THE BRIM, THE UNITS HAVING THE SAME SLOPE OF THEIR CONICAL PORTIONS TO AFFORD A SNUG FIT OF THE UNITS WHEN NESTED IN THE BOREHOLE, AND THE OUTSIDE DIAMETER OF EACH OUTWARDLY EXTENDING BRIM IS ABOUT TWICE THE AXIAL LENGTH OF THE UNIT, THE AXIAL LENGTH OF THE TAMPING PLUG BEING VARIED TO SUIT CONDITIONS BY ASSEMBLING AS MANY OF THE UNITS AS MAY SEEM DESIRABLE FOR THE PARTICULAR BOREHOLE. 